Altered activation of the dorsal anterior cingulate cortex during oddball performance in individuals at risk for Alzheimer's disease.

INTRODUCTION: The neural mechanisms underlying neurodegenerative disorders in the elderly remain elusive, despite extensive neuroimaging research in recent decades. Amnestic type mild cognitive impairment (aMCI) and late-life major depressive disorder (MDD) are two such conditions characterized by intersecting cognitive and affective symptomatology, and they are at a higher risk for Alzheimer's disease. MATERIALS AND METHODS: This study analyzed the neural underpinnings of cognitive and depressive symptoms in a cohort comprising 12 aMCI subjects, 24 late-life MDD patients, and 26 healthy controls (HCs). Participants underwent a detailed neuropsychological assessment and completed a visual attentional oddball task during functional magnetic resonance imaging (fMRI), with evaluations at baseline and at 2-year follow-up. RESULTS: Initial findings showed that aMCI subjects had reduced dACC activation during oddball (target) stimulus detection, a pattern that persisted in longitudinal analyses and correlated with cognitive functioning measures. For HCs, subsequent dACC activation was linked to depression scores. Furthermore, in the affective-cognitive altered groups, later dACC activation correlated with oddball and memory performance. CONCLUSIONS: These findings enhance our comprehension of the neurobiological basis of cognitive and depressive disturbances in aging, indicating that dACC activation in response to a visual attentional oddball task could serve as a neural marker for assessing cognitive impairment and depression in conditions predisposing to Alzheimer's disease.

Effective connectivity of the locus coeruleus in patients with late-life Major Depressive Disorder or mild cognitive impairment.

INTRODUCTION: We compared effective connectivity from the locus coeruleus (LC) during the resting-state in patients with late-life Major Depressive Disorder (MDD), individuals with amnestic Mild Cognitive Impairment (aMCI), and Healthy Controls (HCs). PARTICIPANTS: 23 patients with late-life MDD, 22 patients with aMCI, and 28 HCs. MATERIAL AND METHODS: Participants were assessed in two time-points, 2 years apart. They underwent a resting-state functional magnetic resonance imaging and a high-resolution anatomical acquisition, as well as clinical assessments. Functional imaging data were analyzed with dynamic causal modeling, and parametric empirical Bayes model was used to map effective connectivity between 7 distinct nodes: 4 from the locus coeruleus and 3 regions displaying gray matter decreases during the two-year follow-up period. RESULTS: Longitudinal analysis of structural data identified three clusters of larger over-time gray matter volume reduction in patients (MDD+aMCI vs. HCs): the right precuneus, and the visual association and parahippocampal cortices. aMCI patients showed decreased effective connectivity from the left rostral to caudal portions of the LC, while connectivity from the left rostral LC to the parahippocampal cortex increased. In MDD, there was a decline in effective connectivity across LC caudal seeds, and increased connectivity from the left rostral to the left caudal LC seed over time. Connectivity alterations with cortical regions involved cross-hemisphere increases and same-hemisphere decreases. CONCLUSIONS: Our discoveries provide insight into the dynamic changes in effective connectivity in individuals with late-life MDD and aMCI, also shedding light on the mechanisms potentially contributing to the onset of neurodegenerative disorders.

Antifungal potential of biosurfactants produced by strains of Bacillus spp. (Bacillales: Bacillaceae) selected by molecular screening / Potencial antifúngico de biosulfactantes producidos por cepas de Bacillus spp. (Bacillales: Bacillaceae) seleccionadas por tamizaje molecular

Introduction: Bacillus species are used as biological controllers for phytopathogenic fungi, and the mechanisms to produce controllers include biosynthesis of lipopeptide biosurfactants with antifungal activity. Objective: To evaluate the antifungal potential of the biosurfactants produced by Bacillus strains, selected by molecular screening, on Fusarium oxysporum. Methods: We selected four molecular markers, related to the biosynthesis of surfactin, fengicin, and lichenysin (srfA, spf, fenB, LichAA) in nine Bacillus strains. We used two mineral media with several culture conditions, for biosurfactant production, and a well diffusion test for antifungal potential. Results: Only the biosurfactant produced by UFAB25 inhibits the mycelial growth of F. oxysporum (44 % ± 13): this biosurfactant was positive for srfA, spf, and fenB genes involved in the synthesis of surfactin and fengicine. Antifungal activity depends on culture conditions and the strain. Conclusions: Genetic markers are useful to detect strains with antifungal potential, facilitating the selection of bio-controllers. The biosurfactant profile is influenced by the strain and by culture conditions.

Introducción: Especies de Bacillus han sido empleadas como controladores biológicos contra hongos fitopatógenos. Entre los mecanismos utilizados se destaca la biosíntesis de biosurfactantes lipopeptídicos con actividad antifúngica. Objetivo: Evaluar el potencial antifúngico de los biosurfactantes producidos por cepas Bacillus nativas, previamente seleccionadas mediante tamizaje molecular, sobre Fusarium oxysporum. Métodos: Se utilizaron cuatro marcadores moleculares, relacionados con la biosíntesis de surfactina, fengicina y liquenisina (srfA, spf, fenB, LichAA) sobre nueve cepas de Bacillus. Se utilizaron dos medios minerales con diferentes condiciones de cultivo para la producción del biosurfactante. Se evaluó el potencial antifúngico de los biosurfactantes mediante la prueba de difusión en pozos. Resultados: Se determinó que solo el biosurfactante producido por UFAB25 actúa como inhibidor del crecimiento micelial de Fusarium oxysporum (43.6 % ± 13), esta cepa es positiva para los genes srfA, spf y fenB, involucrados en la síntesis de surfactina y fengicina. La actividad antifúngica depende de las condiciones de cultivo y la cepa. Conclusiones: Los marcadores genéticos ayudan a detectar cepas con potencial antifúngico, facilitando la selección de biocontroladores. El perfil del biosurfactante está influenciado no solo por la cepa, sino también por las condiciones del cultivo.

Phylodynamics and Coat Protein Analysis of Babaco Mosaic Virus in Ecuador.

Babaco is a fast-growing herbaceous shrub with great commercial potential because of the organoleptic properties of its fruit. Babaco mosaic virus (BabMV) is a potexvirus in the family Alphaflexiviridae affecting babaco in all the provinces that produce this crop in Ecuador. BabMV was recently described but it has been affecting babaco for decades and, since many potexviruses are serologically indistinguishable, it may have been previously misidentified as papaya mosaic virus. Based on the coat protein (CP) gene, we aimed to study the distribution and epidemiological patterns of BabMV in babaco and chamburo over the years and to model its three-dimensional structure. Sequences of the CP were obtained from thirty-six isolates from plants collected in the main babaco-producing provinces of Ecuador between 2016 and 2021. The evolution rate of BabMV was estimated at 1.21 × 10-3 nucleotide substitutions site-1 year-1 and a time of origin of the most recent common ancestor around 1958.80. From molecular dynamics simulations, compared to other proteins of BabMV-RDRP, TGB1, and Alkb domain-the CP exhibited a higher flexibility with the C and N terminals as the most flexible regions. The reconstructed viral distribution provides dispersion patterns which have implications for control approaches of BabMV.

Marine heatwaves drive recurrent mass mortalities in the Mediterranean Sea.

Climate change is causing an increase in the frequency and intensity of marine heatwaves (MHWs) and mass mortality events (MMEs) of marine organisms are one of their main ecological impacts. Here, we show that during the 2015-2019 period, the Mediterranean Sea has experienced exceptional thermal conditions resulting in the onset of five consecutive years of widespread MMEs across the basin. These MMEs affected thousands of kilometers of coastline from the surface to 45 m, across a range of marine habitats and taxa (50 taxa across 8 phyla). Significant relationships were found between the incidence of MMEs and the heat exposure associated with MHWs observed both at the surface and across depths. Our findings reveal that the Mediterranean Sea is experiencing an acceleration of the ecological impacts of MHWs which poses an unprecedented threat to its ecosystems' health and functioning. Overall, we show that increasing the resolution of empirical observation is critical to enhancing our ability to more effectively understand and manage the consequences of climate change.

Lower Locus Coeruleus MRI intensity in patients with late-life major depression.

BACKGROUND: The locus coeruleus (LC) is the major noradrenergic source in the central nervous system. Structural alterations in the LC contribute to the pathophysiology of different neuropsychiatric disorders, which may increase to a variable extent the likelihood of developing neurodegenerative conditions. The characterization of such alterations may therefore help to predict progression to neurodegenerative disorders. Despite the LC cannot be visualized with conventional magnetic resonance imaging (MRI), specific MRI sequences have been developed to infer its structural integrity. METHODS: We quantified LC signal Contrast Ratios (LCCRs) in late-life major depressive disorder (MDD) (n = 37, 9 with comorbid aMCI), amnestic Mild Cognitive Impairment (aMCI) (n = 21, without comorbid MDD), and healthy controls (HCs) (n = 31), and also assessed the putative modulatory effects of comorbidities and other clinical variables. RESULTS: LCCRs were lower in MDD compared to aMCI and HCs. While no effects of aMCI comorbidity were observed, lower LCCRs were specifically observed in patients taking serotonin/norepinephrine reuptake inhibitors (SNRIs). CONCLUSION: Our results do not support the hypothesis that lower LCCRs characterize the different clinical groups that may eventually develop a neurodegenerative disorder. Conversely, our results were specifically observed in patients with late-life MDD taking SNRIs. Further research with larger samples is warranted to ascertain whether medication or particular clinical features of patients taking SNRIs are associated with changes in LC neurons.

Locus coeruleus connectivity alterations in late-life major depressive disorder during a visual oddball task.

The Locus Coeruleus (LC) is the major source of noradrenergic neurotransmission. Structural alterations in the LC have been observed in neurodegenerative disorders and at-risk individuals, although functional connectivity studies between the LC and other brain areas have not been yet performed in these populations. Patients with late-life major depressive disorder (MDD) are indeed at increased risk for neurodegenerative disorders, and here we investigated LC connectivity in late-life MDD in comparison to individuals with amnestic type mild cognitive impairment (aMCI) and healthy controls (HCs). We assessed 20 patients with late-life MDD, 16 patients with aMCI, and 26 HCs, who underwent a functional magnetic resonance scan while performing a visual oddball task. We assessed task-related modulations of LC connectivity (i.e., Psychophysiological Interactions, PPI) with other brain areas. A T1-weighted fast spin-echo sequence for LC localization was also obtained. Patients with late-life MDD showed lower global connectivity during target detection in a cluster encompassing the right caudal LC. Specifically, we observed lower LC connectivity with the left anterior cingulate cortex (ACC), the right fusiform gyrus, and different cerebellar clusters. Moreover, alterations in LC-ACC connectivity correlated negatively with depression severity (i.e., Geriatric Depression Scale and number of recurrences). Reduced connectivity of the LC during oddball performance seems to specifically characterize patients with late-life MDD, but not other populations of aged individuals with cognitive alterations. Such alteration is associated with different measures of disease severity, such as the current presence of symptoms and the burden of disease (number of recurrences).

Brain alterations in low-frequency fluctuations across multiple bands in obsessive compulsive disorder.

The extent of functional abnormalities in frontal-subcortical circuits in obsessive-compulsive disorder (OCD) is still unclear. Although neuroimaging studies, in general, and resting-state functional Magnetic Resonance Imaging (rs-fMRI), in particular, have provided relevant information regarding such alterations, rs-fMRI studies have been typically limited to the analysis of between-region functional connectivity alterations at low-frequency signal fluctuations (i.e., <0.08 Hz). Conversely, the local attributes of Blood Oxygen Level Dependent (BOLD) signal across different frequency bands have been seldom studied, although they may provide valuable information. Here, we evaluated local alterations in low-frequency fluctuations across different oscillation bands in OCD. Sixty-five OCD patients and 50 healthy controls underwent an rs-fMRI assessment. Alterations in the fractional amplitude of low-frequency fluctuations (fALFF) were evaluated, voxel-wise, across four different bands (from 0.01 Hz to 0.25 Hz). OCD patients showed decreased fALFF values in medial orbitofrontal regions and increased fALFF values in the dorsal-medial prefrontal cortex (DMPFC) at frequency bands <0.08 Hz. This pattern was reversed at higher frequencies, where increased fALFF values also appeared in medial temporal lobe structures and medial thalamus. Clinical variables (i.e., symptom-specific severities) were associated with fALFF values across the different frequency bands. Our findings provide novel evidence about the nature and regional distribution of functional alterations in OCD, which should contribute to refine neurobiological models of the disorder. We suggest that the evaluation of the local attributes of BOLD signal across different frequency bands may be a sensitive approach to further characterize brain functional alterations in psychiatric disorders.

Does an intracanal composite anchorage replace posts?

OBJECTIVES: This study aims to assess the effectiveness of an intracanal composite anchorage to replace conventionally cemented titanium or bonded glass fibre posts. MATERIALS AND METHODS: Post space preparation was performed up to depths of 6 mm (groups 1 and 2) and 3 mm (group 3) in root filled mandibular premolars. In group 1, titanium posts were cemented with zinc phosphate cement. Glass fibre posts were adhesively cemented in group 2 using a dual-cure composite resin. In group 3, intracanal anchorage was solely performed with a dual-cure composite. All teeth were restored with standardised direct composite crowns without a ferrule. After thermo-mechanical loading, static load was applied until failure. Fracture patterns were assessed, and a microscopic analysis was performed to analyse the occurrence of additional cracks. RESULTS: Group 2 revealed a significantly higher median fracture value (408 N) than groups 1 and 3, while no difference was detected between group 1 (290 N) and group 3 (234 N) (p = .1417). In group 3, the more favourable fracture patterns were observed. However, the majority of teeth within this fracture category revealed additional minor cracks of the root. CONCLUSIONS: Within the limitations of this study, adhesive intracanal anchorage to a depth of 3 mm with resin composite only has the same fracture resistance as titanium posts conventionally cemented to a depth of 6 mm. Even teeth with repairable main fractures exhibited additional dentinal cracks on the root. CLINICAL RELEVANCE: Additional dentinal root cracks in the teeth with repairable main fractures may considerably impair their longevity.